Field of the Invention
The present invention relates to an illumination optical apparatus and a device manufacturing method.
Description of the Related Art
An exposure apparatus for use in manufacturing of a semiconductor device or the like transfers a pattern formed on an original plate (a reticle, a mask or the like) to a substrate (a wafer or the like on a surface of which a resist layer is formed) via an image forming optical system, a projection optical system, or the like. The exposure apparatus includes an illumination optical apparatus for illuminating the original plate with an optical flux from a light source. When the illumination light for the original plate of the illumination optical apparatus is not uniform or the telecentricity (a degree of parallelism between an optical axis and a main light beam) collapses, the pattern transfer to the substrate is insufficient and it is difficult for the exposure apparatus to provide a high-quality device. If the telecentricity collapses, a position at which an image is formed on the original plate is laterally shifted when the original plate is exposed at a position shifted with respect to the optical axis. When the telecentricity differs according to an image height, a distorted image is formed in the original plate. In any case, it is difficult to faithfully transfer a pattern of the original plate to the substrate. Therefore, improvement of luminance uniformity and adjustment of telecentricity are necessary in the illumination optical apparatus.
As a method of improving luminance uniformity, an illumination optical apparatus having an optical integrator is known. An inner surface reflection type optical integrator causes a light intensity distribution to be uniform in an emission end surface by reflecting an optical flux incident from an incident end surface in an inner surface a plurality of times. Further, it is possible to improve luminance uniformity in a surface to be illuminated by disposing an image forming optical system between the emission end surface and the surface to be illuminated so that the emission end surface and the surface have a conjugate relation.
On the other hand, a method of adjusting the telecentricity is disclosed in Japanese Patent Laid-Open No. 2002-50564. In an illumination optical apparatus disclosed in Japanese Patent Laid-Open No. 2002-50564, an emission end surface of an inner surface reflection type optical integrator and an incident end surface of a wave front division type optical integrator are connected to have a conjugate relation according to an image forming optical system. The telecentricity is adjusted by causing the inner surface reflection type optical integrator to have parallel eccentricity and changing a luminance distribution in an incident end surface of the wave front division type optical integrator. In addition, in the image forming optical system disclosed in Japanese Patent No. 5036429, the telecentricity is adjusted by changing the luminance distribution in a pupil surface using a method of shifting an optical beam transmitted through a pupil surface within the image forming optical system, a method of limiting a transmission region by shielding a part within an effective system of the pupil surface, or the like.
However, in the illumination optical apparatus disclosed in Japanese Patent Laid-Open No. 2002-50564, it is also necessary to provide the wave front division type optical integrator and the size and cost of the illumination optical apparatus increase. In addition, because it is necessary to form a good pupil surface within the image forming optical system in the image forming optical system disclosed in Japanese Patent No. 5036429, the image forming optical system is complex and the size and cost of the illumination optical apparatus increase.